In the field of machine-readable information code, the bar code is one of the most widely recognized by reason of being used on numerous consumer articles and in other applications. One bar code, being the universal product code (UPC), includes different width bars which are spaced one from another in an overall pattern on a consumer article for scanning along a path of travel by a moving reader or sensor. Contrariwise, the path of travel of a consumer article carrier with respect to a reader or sensor could be used wherein the reader or sensor is maintained stationary for scanning articles moving therepast. The different width vertical bars and the spaces therebetween make up the UPC scannable symbol, and optical font characters make up the corresponding human-readable characters. The vertical bars and spaces reflect light emitted by an optical scanner which reads the symbol-marked products--such UPC symbol identifying the manufacturer and the product.
Machine readable codes may also be triangular-shaped of equal length bars or they may be of unequal length wherein the sensor identifies characters by reading along the triangles or across the various lengths thereof.
Another form of bar code is the color bar code which may consist of black, green, and white bars arranged in various patterns for representing characters.
A further type of code includes the optical character recognition type (OCR) which may be both machine and human-readable and is utilized where both readings are desirable.
Another code pattern utilizes a matrix which may consist of squares, dots, circles or like indicia which is machine-readable and which is useful for identifying and printing of characters.
The above codes are generally formed along a line wherein the reader or sensor follows a straight path across the code wherein the code is directed and disposed in a path along a line coinciding with the direction of movement and viewing of the sensor. In most prior art codes, the entire pattern usually must be sensed and the relation between the pattern and the sensor usually must be fixed to properly recognize the characters, however, the hand held wand readers allow some variation from a fixed path or line of travel.
The basic concept underlying recording is the creation of patterns in or on a record medium so that one or more patterns can be taken to represent one or more characters. The patterns are sequentially detected by appropriate sensor arrays when there is relative motion between the record medium and the array.
Many applications exist for the several printed codes mentioned above, which codes have high information density and are machine readable. While none of such codes can be used for all applications, the following parameters or requirements specify a particular code for very wide usage. The code should be high density for printing of at least ten alphanumeric characters per linear inch, the code should be readable with a light weight, low cost, and preferably hand-held wand, and the first pass read rate should be at least or greater than 95%. The character substitution error rate should be less than one in ten million after all error detection and error correction has taken place, and the code should be printable with a low cost, computer controlled, widely available printer such as a dot matrix printer.
A dot matrix printer is defined as one capable of printing dots on a record medium at selected points on an X-Y grid and representative types of such printers include a wire or needle matrix impact printer, a thermal non-impact printer, or an ink jet non-impact printer. Some of these printers utilize dual grids in which characters are located on a coarse grid having center-to-center spacing 0.1 inch horizontal and 0.16 inch vertical, while within a character, dots are located on a fine grid with both horizontal and vertical spacing of 0.015 inch with typical characters printed at seven dots high and five dots wide.
In many cases of the prior art, when the reading depends essentially on multiple sensing elements, it is seen that the code scheme requires that the reader or sensor array have elements in an order where any one element always senses the same portion of the particular pattern, or stated differently, the allowable unwanted lateral displacement of the sensor with respect to the record medium must be kept less than the lateral dimension of a sensing element--the lateral dimension being along a direction perpendicular to the relative motion of the medium and the sensor. In specific applications, for example, where the reader and the symbols are under machine control, the reader (read head) must read the same track on magnetic tape, or the photocell or contact must read the same bit of each character on paper tape. That is, the sensor array must be properly aligned with respect to the pattern so that there is no ambiguity about the meaning of the signal coming from each element of the array.
Representative prior art which is considered relevant to the subject matter of the present invention includes U.S. Pat. No. 3,532,859, issued to J. Laplume on Oct. 6, 1970, which discloses an identifying system using optical codes wherein a plate or card comprises a plurality of squares in characteristic binary code patterns of non-reflective and reflective surfaces. The reflective surfaces may comprise a multiplicity of small spherical beads or a multiplicity of convex elements alongside the non-reflective or light-absorbing surfaces and be read or sensed by an illuminating and sensing unit.
U.S. Pat. No. 3,558,859, issued to F. W. Dilsner et al. on Jan. 26, 1971, shows an automatic reading system for record media having encoded data of perforated and of printed codes. The perforated code includes legible and illegible type arranged in a matrix pattern and the printed code includes a bar code and a marking code.
U.S. Pat. No. 3,860,790, issued to S. J. Reckdahl on Jan. 14, 1975, shows a data processing form which has a plurality of printed indication areas for use with optical sensing apparatus. Printed symbols extend uniformly within a certain dimension and have a printed area of an optical density which is selected in relation to the sensing means.
U.S. Pat. No. 3,898,434, issued to A. G. Bigelow et al. on Aug. 5, 1975, discloses a machine-readable coded member formed of pattern areas with each area corresponding to a character. Each area is divided equally into rectangular portions and the presence or absence of indicia in selected portions represents a designated character. At least two pattern portions of each area are aligned along a path of travel of the coded member with respect to the scanner or reader and an index mark is placed on a line which is perpendicular to the path of travel of the document.
U.S. Pat. No. 4,114,033, issued to A. Okamoto et al. on Sept. 12, 1978, discloses a number of bar codes recorded in dual directions on an information card. A plurality of bar codes comprising one group bar code are arranged in one direction which is orthogonal to the bar symbol and a plurality of group bar codes are arranged in the other direction in which the bar symbol extends. The group bar codes are sequentially scanned for the recognition thereof.
And, U.S. Pat. No. 4,130,243, issued to R. L. Stevens on Dec. 19, 1978, discloses a machine-readable optical printed symbol format that is generally hour-glass shaped and consists of nine elements of alternate bars and spaces vertically arranged in a manner wherein the length of the bars and the spaces is greater at the top and bottom of the symbol and decreases to a minimum point at the middle of the symbol.